Quiton Raimi L, Greenspan Joel D
Program in Neuroscience, Department of Biomedical Sciences, Dental School, and Research Center for Neuroendocrine Influences on Pain, University of Maryland, Baltimore, MD, United States.
Pain. 2007 Nov;132 Suppl 1(Suppl 1):S134-S149. doi: 10.1016/j.pain.2007.09.001. Epub 2007 Oct 24.
Sex differences in endogenous pain modulation were tested in healthy volunteers (32 men, 30 women). Painful contact heat stimuli were delivered to the right leg alone, and then in combination with various electrical conditioning stimuli delivered to the left forearm. Four conditioning protocols were applied to each subject in separate sessions: mild, non-painful (control); distracting; stressful-yet-non-painful; strongly painful. Thermal stimuli were rated on visual analog scales for pain intensity (INT) and unpleasantness (UNP). Distracting and painful conditioning stimuli significantly reduced heat pain INT and UNP ratings for both sexes, with significantly larger distraction effects on INT ratings for men than women (p=0.004). No sex differences in pain-evoked hypoalgesia were detected (p>0.05). The stress protocol did not consistently reduce heat pain ratings, possibly because the protocol was not sufficiently stressful to activate endogenous modulatory systems. Regression analysis revealed that the magnitude of pain-evoked hypoalgesia was predicted by the perceived distraction (p=0.003) and stress (p=0.04) produced by the painful conditioning stimulation, providing evidence that distraction and stress contribute to pain-evoked hypoalgesia. However, the contribution of stress to pain-evoked hypoalgesia differed by sex (p=0.02), with greater perceived stress associated with greater hypoalgesia in men and the opposite trend in women, suggesting sex differences in the mechanisms underlying pain-evoked hypoalgesia. This study provides indirect evidence that multiple neural mechanisms are involved in endogenous pain modulation and suggests that sex-specific aspects of these systems may contribute to greater pain sensitivity and higher prevalence of many chronic pain conditions among women.
在健康志愿者（32名男性，30名女性）中测试了内源性疼痛调节的性别差异。仅对右腿施加疼痛性接触热刺激，然后结合对左前臂施加各种电调节刺激。在单独的 sessions 中对每个受试者应用四种调节方案：轻度、非疼痛性（对照）；分散注意力；有压力但非疼痛性；强烈疼痛。热刺激在视觉模拟量表上对疼痛强度（INT）和不愉快程度（UNP）进行评分。分散注意力和疼痛性调节刺激显著降低了男女的热痛INT和UNP评分，男性对INT评分的分散效应显著大于女性（p = 0.004）。未检测到疼痛诱发的痛觉减退存在性别差异（p>0.05）。应激方案并未持续降低热痛评分，可能是因为该方案的压力不足以激活内源性调节系统。回归分析显示，疼痛诱发的痛觉减退程度可由疼痛性调节刺激产生的感知分散（p = 0.003）和压力（p = 0.04）预测，这证明分散注意力和压力有助于疼痛诱发的痛觉减退。然而，压力对疼痛诱发的痛觉减退的贡献因性别而异（p = 0.02），男性中感知到的压力越大，痛觉减退越明显，而女性则相反，这表明疼痛诱发的痛觉减退背后的机制存在性别差异。这项研究提供了间接证据，表明多种神经机制参与内源性疼痛调节，并表明这些系统的性别特异性方面可能导致女性对疼痛更敏感以及许多慢性疼痛疾病的患病率更高。
